A camera, sometimes referred to as an imaging apparatus, includes one or more imaging elements such as a complementary metal oxide semiconductor (CMOS) imaging sensors, and converts light received by the one or more imaging elements into an image signal. The camera may also calculate an exposure value to correct an exposure based on a luminosity value, conduct an adjustment of a setting value of a shutter speed and a diaphragm value, etc., in accordance with a program chart of the exposure value.
Some cameras include an automatic exposure (AE) control function that automatically conducts an exposure adjustment.
A luminosity value is a value which represents a degree of luminous intensity of an image, the exposure is to expose the imaging elements to light, and the correct exposure is exposure as images that represent a natural luminous intensity and color when people see the images. The exposure value is a value representing a degree of exposure of the imaging elements to light. The shutter speed is a time (exposure time) in which the imaging elements are exposed to light by the opening of a shutter which opens and closes to interrupt light. The diaphragm value is the value of luminous intensity which is images appearing in the imaging elements and may be referred to as F-number. The program chart is a correspondence table including information that correlates exposure value, shutter speed and diaphragm value.
When the luminosity of an object becomes high, the AE control function conducts a control process in which the shutter speed is increased (made fast) and the diaphragm is decreased (made small). However, some cameras are not equipped with a diaphragm mechanism because such mechanisms increase cost, in such low-cost cameras, an exposure control is performed by only adjusting the shutter speed (Refer to Japanese Patent Application Laid-open no. H2-288560 and Pat. No. 3,778,114).
When capturing video, it is necessary to conduct a precise exposure control so as to smoothly transition between frames. Generally, as shutter speed increases, a speed of resolution of a CMOS imaging sensor decreases. However, conventional cameras cannot accurately perform such precise exposure control with a high shutter speed in an environment when luminosity of an object is high. Accordingly, such an imaging apparatus and control method to conduct precise exposure control are desired.